Neutral Admittance Characteristics - ABB 615 series Technical Manual

Section 4
Protection functions
4.2.4.5
386
time setting, the TRIP output is activated. If the fault disappears before the module
operates, the reset timer is activated. If the reset timer reaches the value set with the Reset
delay time setting, the operation timer resets and the PICKUP output is deactivated. The
timer calculates the pickup duration value PICKUP_DUR, which indicates the percentage
ratio of the pickup situation and the set trip time. The value is available in the monitored
data view.
Blocking logic
There are three operation modes in the blocking function. The operation modes are
controlled by the BLOCK input and the global setting in Configuration/System/Blocking
mode which selects the blocking mode. The BLOCK input can be controlled by a binary
input, a horizontal communication input or an internal signal of the protection relay's
program. The influence of the BLOCK signal activation is preselected with the global
setting Blocking mode.
The Blocking mode setting has three blocking methods. In the "Freeze timers" mode, the
operation timer is frozen to the prevailing value, but the TRIP output is not deactivated
when blocking is activated. In the "Block all" mode, the whole function is blocked and the
timers are reset. In the "Block TRIP output" mode, the function operates normally but the
TRIP output is not activated.

Neutral admittance characteristics

The applied characteristic should always be set to cover the total admittance of the
protected feeder with a suitable margin. However, more detailed setting value selection
principles depend on the characteristic in question.
The settings defining the admittance characteristics are given in primary
milliSiemens.
The forward and reverse boundary settings should be set so that the forward setting is
always larger than the reverse setting and that there is space between them.
Overadmittance characteristic
The overadmittance criterion is enabled with the setting Operation mode set to "Yo". The
characteristic is a circle with the radius defined with the Circle radius setting. For the sake
of application flexibility, the midpoint of the circle can be moved away from the origin
with the Circle conductance and Circle susceptance settings. Default values for Circle
conductance and Circle susceptance are 0.0 mS, that is, the characteristic is an origin-
centered circle.
Operation is achieved when the measured admittance moves outside the circle.
1MAC059074-MB A
615 series ANSI
Technical Manual